1. Field of the Invention
This invention in general relates to photographic apparatus and in particular to improved cylindrical processing rollers for use in motor driven photographic processing apparatus of the type which spread a fluid processing composition in a thin, substantially uniform layer between selected layers of integral type, self-processable film units while advancing a film unit to the exterior of a camera after photoexposure.
2. Description of the Prior Art
Fully automatic photographic cameras which utilize integral type self-processable film units are well-known in the photographic field, having been extensively described in the patent literature and in public use for several years now. These cameras, such as Polaroid Corporation's "SX-70" and "Pronto!" and Eastman Kodak Company's "EK-6" and "EK-8" cameras, are designed to automatically produce furnished, waste-free color prints with virtually no operator involvement other than to compose the picture, perhaps focus, and then actuate the camera by depressing its cycle "start" button.
They accomplish this task through the use of specially designed interdependent function providing subsystems that are organized to carry out a programmed series of sequential operations which produce the finished print.
Once actuated, the order of camera operations begins with exposure of a film unit. Afterwards, the exposed film unit is advanced from its exposure location into engagement with a film processing subsystem or apparatus which initiates a diffusion transfer process for developing and forming a visible image in the film unit while transporting it to the exterior of the camera where it becomes accessible to the photographer.
The film units, as for example those described in considerable detail in U.S. Pat. Nos. 3,415,644; 3,594,165; and 3,761,268, normally contain all the photographic components necessary for the diffusion transfer process. Typically, the film units comprise, in general terms, a pair of superposed sheet elements, at least one being transparent, which serve to support layers of photochemical substances which may comprise photosensitive and image-receiving layers; and, as well, include a rupturable container of viscous processing fluid positioned adjacent a leading edge of the film unit and adapted to have its processing fluid released between the sheet elements to begin the diffusion transfer process. Release of the processing fluid is effected by the processing apparatus which first operates to rupture the container and thereafter causes the released mass of processing fluid to flow between the sheet elements, opposite the direction of travel of the film unit, so that the processing fluid is progressively deposited between the sheet elements as a thin, uniform layer generally coextensive with the exposed area of the film unit. Upon completion of the diffusion transfer process, the final image is viewable through the sheet element which is transparent.
Photographic processing apparatus having the capability of performing the film advancing and fluid spreading operations outlined above are well-known in the art. Generally, such apparatus comprise a pair of rollers rotatably mounted in juxtaposed relation and resiliently urged toward one another to exert a pressure on the film unit as it is advanced between them in response to rotation of at least one of the rollers by a motor drive. The rollers typically are manufactured to precision tolerances so that the fluid layer thickness is properly sized for optimum photographic image quality and at least one of them is provided with a high-friction, sheet-contacting surface to provide a high traction force to transport the film unit to the outside of the camera without slippage and without visably damaging the surfaces of the film unit.
In addition to the precision tolerances and the high-friction, low-abrasion surface characteristic, these rollers must also possess high strength so that they either won't deform under the pressures generated during processing or deform only in a predictable manner, have high corrosion resistance, and be capable of retaining their original geometry after having processed a number of film units related to their expected useful life.
Changes in initial roller geometry can occur by a build up of particulate matter from the film units which is picked up by the roller's surfaces. Thus, a further design requirement on these type of rollers is that they do not pick up particulate matter.
One prior art device which satisfies the functional criteria for such film processing apparatus is described in considerable detail in U.S. Pat. No. 3,776,118 issued to John J. Driscoll et. al. on Dec. 4, 1973 and entitled "Photographic Film Processing Apparatus". Here the processing apparatus includes a roller assembly having first and second rotatably mounted juxtaposed elongated rollers which are resiliently urged toward one another. A pair of annular collars are provided on the first roller to define a minimum gap between the rollers to facilitate the initial introduction of the leading edge of a film unit between the rollers. The first roller is adapted to be selectively driven by a motor of the camera and, when so driven, its annular collars impart a rotary motion to the second roller. At least those portions of the two rollers adapted to contact one another are formed of a relatively low friction, impact resistant material, such as stainless steel, while at least the sheet-contacting facing surface of the first roller is formed of a relatively high friction material such as urethane. The urethane which is coated on the first roller operates to provide the relatively high traction force between the first roller and the film unit to transport the film unit outside of the camera and the stainless steel provides the strength necessary to withstand the pressures generated during the transport and fluid spreading phases. In addition to its strength, the stainless steel also possesses desirable corrosion resistant characteristics.
Although the performance of this type device is more than adequate as evidenced by its success in Polaroid Corporation's "SX-70" and "Pronto!" cameras, it is, as one would expect from its design criteria, relatively expensive to manufacture. The urethane coating coupled with the precision tolerances in particular represent a major portion of its cost.
Another motor driven processing apparatus is that used in Eastman Kodak Company's "EK-6" and "EK-8" cameras. Here both rollers, which appear to be surfacehardened steel, are motor driven and each has a roughened surface to provide the high traction force necessary for film transport. It appears that the roughened surfaces of these rollers may be achieved by conventional crush grinding techniques and may afterwards be plated for corrosion protection and wear resistance. The roughened surfaces of these rollers would also appear to be relatively expensive to manufacture.
Consequently, there is a need for an improved, less expensive, photographic processing roller which can be used with integral type, self-processable film units. Thus, it is a primary object of the present invention to provide such a roller by using electrical discharge machining (EDM) techniques to texture its surface to achieve the high-friction, low-abrasion surface required of these type rollers.
It is recognized that EDM textured roller surfaces have been used extensively in the steel industry for the purpose of texturing sheet steel (U.S. Pat. Nos. 3,878,353; 3,800,117; and Re 28,027) and that EDM also has been used to increase the friction of rolls used to feed strip stock (U.S. Pat. No. 3,941,970). However, the EDM textured rollers disclosed above are not appropriate for use with self-processable film. Therefore, it is another object of the present invention to provide an improved photographic processing roller having a particular EDM surface which is suitable for use with self-processable film units.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.